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Rooftop Gardens
18 Hydroponics can also solve the problem of 19
how to take advantage of all that terrific
unused space way up there—on rooftops!
Not all rooftops can handle a heavy load of
dense soil. But hydroponics can lighten the
load by using lighter materials or shallow
water beds.
20
In Tokyo, two telecommunications
companies sponsored the planting of
sweet potatoes in rooftop gardens. They
called this project Green Potato. The wide
leaves of the plants were so effective at
transpiration that the leaf-covered areas
were more than 68 degrees Farenheit
(20 degrees Celsius) cooler than the areas
not covered by leaves.
21
“ Hydroponics can also solve the
problem of how to take advantage
of all that terrific unused space way
up there—on rooftops!”
myNotes
Rooftops get screamingly hot in the
summertime—up to 90 degrees Farenheit
(32 degrees Celsius) warmer than the air.
But a green roof can actually be cooler
than the air. That’s because plants do a
“cool” thing called transpiration. They take
water in through their roots and then
release it through their leaves. The heat
from the air is used to evaporate the water,
bringing temperatures down.
The idea is clearly catching on. A group
called the Rooftop Garden Project has
greened roofs all over Montreal and has
begun sharing its techniques with people in
other countries. They’ve even taken their
skills to Haiti to help establish urban
agriculture there in the aftermath of the
2010 earthquake.
In Chicago, the Gary Comer Youth
Center occupies a building that used to be
an abandoned warehouse. It’s a huge,
reinforced structure topped by a
906-square-yard (800 square meter)
rooftop garden. The soil for the garden is
18 inches (46 centimeters) deep and grows
an amazing 1,000 pounds (454 kilograms)
of organic vegetables per year. The produce
is brought home by the volunteer
gardeners and is used in the center’s
cooking classes.
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